Corner grinding mechanism and method



Feb. 26, 1957 B. D. ROBBINS CORNER GRINDING MECHANISM AND METHOD 2 Sheets-Sheet 1 Filed Dec. 11, 1952 m a L r M 9- 14 L,

Q INVENTOR m Bruce D.Robbxns (QM $41M ATTORNEY Feb. 26, 1957 B. D. ROBBINS CORNER GRINDING MECHANISM AND METHOD 2 Sheets-Sheet 2 Filed Dec. 11, 1952 INVENTOR Bruce D.Robbi.ns

BY @160 g ATTORNEY United States Patent CORNER GRINDING MECHANISM AND METHOD Bruce D. Robbins, Arnold, Pa., assignor to Pittsburgh Plate Glass Company, Allegheny County, Pa., a corporation of Pennsylvania Application December 11, 1952, Serial No. 325,296

3 Claims. (Cl. 511ll1) This invention relates to machines for edge grinding glass plates or the like, and more particularly to a corner portion grinding attachment for use on such machines.

Machines for edge grinding glass plates such as vehicle windows and ventilators are well known. Such machines provide for rough and finish grinding of the edges of glass plates, and utilize rotary abrading units mounted for movement against the edges of the glass plates and guided by segmental pattern cams. One such edge grinding machine is illustrated in United States Letters Patent No. 2,597,180, dated May 20, 1952. The present invention is concerned with an attachment for such a grinding machine.

One object of this invention is the provision of a corner portion grinding attachment for a rotary edge grinding machine.

Another object of this invention is the provision of an automatic corner portion grinding attachment for window and ventilator edge grinding machines.

A further object of this invention is the provision of an economical corner portion nipper attachment for camguided edge grinding machines, which attachment eliminates the need of expensive segmental corner cams in such machines.

A still further object of this invention is the provision of a corner portion nipper attachment which may be easily installed on rotary edge grinding machines already In use.

Other objects and advantages of the invention will become more apparent from the following detailed description of a preferred embodiment thereof.

In the drawings, Figure l is an elevational view, partly cut away and partly diagrammatic, of a rotary edge grinding machine having a corner grinding attachment applied thereto.

Figure 2 is a plan view, partly cut away and partly diagrammatic of the machine and attachment shown in Figure 1.

Figure 3 is a perspective view of a portion of the corner grinding attachment supporting shaft.

Referring to the drawings, the base frame of the rotary edge grinding machine is designated by the numeral 10. A pedestal 11 is mounted on the base 10, and a table 12 is supported by the pedestal for rotation about a vertical axis. Drive means for rotating the table 12 form no part of this invention, and may be of the type disclosed in the above-mentioned Patent No. 2,597,180. The rotary table 12 is provided with parallel annular surfaces 14 and 15, the upper surface 14 being for the support of pieces of glass 16 having edges to be ground. The lower surface has segmental templates 17 secured thereon, the templates 17 being provided to control the action of the edge grinding mechanism hereinafter described. The rotary table 12 is also provided with a head 18 which rotates with the table 12 and carries a series of fluid-operated clamping devices 19. The clamping devices 19 hold the glass pieces 16 against the table surface 14 during the grinding operations. A pair of Patented Feb. 26, 1957 standards 25 are secured to the base 10, one at either side of the rotary table 12, and the standards are cross-connected at their tops by a cross piece 26.

Edge grinding units, such as unit 30, are supported circumferentially of the table 12, by means of a yoke 31. The yoke 31 is supported by and journaled in the top of standard 25 for limited rotary movement on a vertical The edge grinding unit 30 is pivotally supported by the outer end of a yoke 31 and comprises a pair of grinding wheels 32 belt-driven by a pair of electric motors 33. Each grinding wheel 32 is mounted for rotation on a vertical axis, and a template wheel 34 for and below each grinding wheel 32 is carried by the grinding unit and mounted for rotation on a vertical axis alined with the axis of its adjacent grinding wheel. The template wheel 34 is adapted to engage the periphery of the template 17 to control the contact of the grinding wheel 32 with the edge of the glass pieces 16. As shown in dotted lines in Figure 2, the glass pieces 16 may be of the outline shape used for the ventilator windows of automobiles. T he grinding unit 30 may be biased toward the periphery of the rotary table to hold the grinding wheels and template wheels against the glass to be ground and the template by means of cables, pulleys and weights as shown in the above mentioned Patent No. 2,597,180. The structure described thus far is well known, and the details thereof will be Well known to those skilled in the art, or by reference to said issued patent.

The corner portion grinding attachment of this invention is applicable to an edge grinding machine of the above character. The corner portion grinding attachment includes a relatively small diameter diamond type grinding wheel 40 journaled in the outer end of an arm 41 which is secured to and projects outward from a ver tical shaft 42. The shaft 42 is journaled in suitable supporting bearing 43 secured to the base of standard 25. The grinding wheel 40 is rotated by an electric motor 44 mounted on a stationary part of the machine. The motor 44 is connected by a belt 45 to a pulley 46, and pulley 46 is connected to a pulley 47 which is connected by a belt 48 to a pulley 49 on the shaft of grinding wheel 40. The pulleys 46 and 47 are journaled on the arm 41 and in axial alinement with the vertical axis of shaft 42. The lower end of shaft 42 is provided with a lever arm 50 secured to the shaft and projecting outward as shown in Figure 3. A tension spring 51 extends between the end of arm 50 and a bracket 52 secured to the standard 25, and serves to partially rotate the shaft 42 in a direction to cause arm 41 to move the grinding wheel 40 against the work pieces 16. A second lever arm 54 is also secured to the shaft 42 and is connected by rod 55 to a piston in an air cylinder 56. The air cylinder 56 is secured to the base of standard 25. Compressed air from a supply line 57 is admitted to the air cylinder 56 by means of a solenoid operated valve 58. A micro-switch 59 supported from the cross piece 26 in a position to be actuated by movement of a clamping device 19 thereunder is connected to energize a timing device 60 which in turn is connected to control energization of the solenoid valve 58.

When the table 12 rotates a work piece 16 adjacent to the corner portion nipper grinding wheel 40, the housing of the clamping device 19 above the work piece 16 closes the microswitch 59 which starts the timer 60 which causes the solenoid to operate the valve 58. The valve 58 is operated to vent air pressure from the air cylinder 56 and thereby permit the spring 51 to turn the shaft 42 and bias the grinding wheel 40 against the corner portions of the work piece 16. The timer 60 is also connected to cause the motor 44 to be energized during the time the grinding wheel 40 engages the work. The valve 58 may be actuated by the timer 60 to admit air to the air cylinder 56 so as to cause rod 55 to move the arm 41 and hold the grinding wheel 40 away from the work 16 when there are no corners adjacent the grinding wheel 40 for grinding.

The corner portion nipper or grinding wheel 40 is preferably a small diamond type wheel about five inches in diameter, and is used only for grinding the corner portions of glass work pieces 16. The use of such a corner portion grinding attachment eliminates the necessity for expensive corner portion segments for the segmental templates 17, and also reduces wear on the main edge grinding wheels 32.

Although the corner portion grinding mechanism has been specifically described as an attachment for an edge grinding machine of the type disclosed in the mentioned prior patent, it is not intended that this mechanism be considered only an attachment for that machine since it will be obvious to those skilled in the art that the mechanism disclosed may be added to or incorporated in many types of grinding machines without departing from the scope of the invention defined in the accompanying claims.

I claim:

1. In combination with a machine for edge grinding glass plates comprising a relatively large grinding wheel, a rotatable table and means for mounting a glass plate in fixed relation to said rotatable table to rotate an edge thereof past said wheel, a corner grinding attachment comprising an arm pivotally mounted on said machine, a relatively small grinding wheel journaled in said arm, a motor, drive means connecting said motor to said small wheel to rotate the latter, tension means to urge said arm and small wheel toward the edge of the glass plate mounted on said table, power means connected to said arm for moving said arm and small wheel away from said edge, and control means to deactivate said power means when the corners of the edge pass the position to which the small wheel is urged by said tension means when the control means is deactivated.

2. The combination according to claim 1, wherein the rotatable table comprises a plurality of peripherally spaced clamping devices for securing to each one thereof a separate plate for edge grinding.

3. A method of edge grinding a glass plate having an edge including leading and trailing corner portions comprising moving the plate relative to a pair of grinding wheels, urging a first grinding wheel to contact continuously the edge of said plate as the latter moves past said wheel, rotating the first grinding wheel while said edge is moving therepast, moving an additional grinding wheel into engagement with the leading corner portion formed by said edge as the latter passes said additional grinding wheel, removing the additional grinding Wheel from glass edge contact when the leading corner portion has passed the additional grinding wheel, moving the additional grinding wheel into engagement with the trailing corner portion formed by said edge as the latter passes said additional grinding wheel, and rotating said additional grinding wheel while it is contacting said leading and trailing corner portions.

References Cited in the file of this patent UNITED STATES PATENTS 1,958,526 Weber May 15, 1934 2,010,922 Leonard Aug. 13, 1935 2,038,150 Weber Apr. 21, 1936 2,080,280 Klages May 11, 1937 2,527,791 Brink Oct. 31, 1950 2,579,337 Reaser et al. Dec. 18, 1951 2,597,180 Reaser et al. May 20, 1952 

